Method of manufacturing a conduction heater

ABSTRACT

A conduction heater preferably formed as an annular matrix or heater plate for tire recapping and vulcanizing equipment. The heater or matrix is formed by positioning a generally circular hollow tube within an annular cavity, supporting the circular element for sliding movement relative to the cavity, filling the cavity with molten metal, and solidifying the molten metal whereby the relative sliding movement prevents the circular element from rupturing during manufacture and use due to different coefficients of expansion of the material from which the circular element is constructed and the molten metal forming the matrix body upon the solidification thereof. In further accordance with the present method, ends of the circular element are closed by plugs disposed tangentially of the annular cavity whereby upon the solidification of the molten metal and the removal of the plugs thereafter, the ends of the circular element are accessible through tangential voids in a peripheral surface portion of the matrix whereby steam and/or electrical fitments may be secured to the exposed ends of the circular element.

United States Patent [-191 MacMillan [451 Jan. 9,1973

[54] METHOD OF MANUFACTURING A CONDUCTION HEATER [75] Inventor: KennethT. MacMillan, Macon, Ga.

[73] Assignee: MacMillan Mold Company, Inc.,

Macon, Ga.

[22] Filed: Sept. 18, 1970 [21] Appl. No.: 73,509

Primary ExaminerR. Spencer Annear Att0mey-Diller, Brown, Ramik & Holt[57] ABSTRACT A conduction heater preferably formed as an annular matrixor heater plate for tire recapping and vulcanizing equipment. The heateror matrix is formed by positioning a generally circular hollow tubewithin an annular cavity, supporting the circular element for slidingmovement relative to the cavity, filling the cavity with molten metal,and solidifying the molten metal whereby the relative sliding movementprevents the circular element from rupturing during manufacture and usedue to different coefficients of expansion of the material from whichthe circular element is constructed and the molten metal forming thematrix body upon the solidification thereof. In further accordance withthe present method, ends of the circular element are closed by plugsdisposed tangentially of the annular cavity whereby upon thesolidification of the molten metal and the removal of the plugsthereafter, the ends of the circular element are accessible throughtangential voids in a peripheral surface portion of the matrix wherebysteam and/or electrical fitments may be secured to the exposed ends ofthe circular element.

19 Claims, 7 Drawing Figures PATENTEDJAN ems I 3.709.280

' sum 2 or 2 I 1N VENTOR KENNETH T. MacMlLLAN METHOD OF MANUFACTURING ACONDUCTION HEATER It is conventional in the recapping and vulcanizingindustry to employ annular tire molds or matrices which are generally ofan annular configuration defined by inner and outer peripheral surfaceportions, the former of which defines a mold cavity. The cavity isprovided with a desired tread design such that during a recappingoperation, as an example, a tire with camel back thereon when positionedin the cavity and cured will assume the mirror image configuration ofthe tread design.

The curing is generally accomplished by passing steam through ports inthe matrix or connecting embedded heaters in the matrix to a suitablesource of electrical energy. If, as is the usual case, the ports of thematrix are formed by hollow tubes about which has been cast molten metalwhich subsequently is permitted to solidify, the initial heating of thetubes results in the expansion thereof, and after the curing operationcold water introduced into the tubes results in contraction. Where thetubes are constructed from, for example, steel and the matrix casing orbody is formed from aluminum, the difference in the coefficient ofexpansion of these metals results in the rupture of the tubes, and moreparticularly inlet and outlet fitments which are conventionally weldedto the tube ends. Moreover, such relative expansion and contraction caneven fracture the fitments during the molding of the matrices.

It is also the present practice in the industry of curing tires andmatrices by employing either steam or elec- 'tricity, and moreparticularly either by embedding calrod or similar type heaters in thematrix casting or a tube which is adapted for connection to a source ofsteam, hot water or the like. However, at present there are nocommercially available matrices which, at the choice of the user, can bealternatively and selectively heated by electricity, steam, hot water ora similarly heated medium.

In keeping with the foregoing, it is a primary object of the presentinvention to provide a novel heater though particularly designed as anannular heater plate or matrix for the recapping and vulcanizing oftires, is equally applicable for use in other fields. The heater may bedesigned as a frying pan, a percolator or similar heating plate, anelectric iron and most any type heater in which a heating element isnormally cast directly into metal bodies which are to be heated or isinsertable in cast metal bodies having appropriate openings to receivethe heater elements.

Turning first to the objects of the method of manufacturing the novelheating device of the present invention, a mold is provided'having acavity of a predetermined configuration in which is positioned anelement supported for sliding movement relative to the mold cavity. Thecavity is then filled with molten metal, and during the filling,solidification, and subsequent use of the heating device, the slidingmovement between the casting or heater body and the element preventsrupture of the latter due to any differential expansion and/orcontraction due to different coefficients of expansion of the metalsforming the casting and the element.

A further object of this invention is to provide a novel method of thetype aforesaid wherein the cavity is of an annular configuration, theelement is of a generally circular configuration, and ends of thecircular element project tangentially outwardly of the cavity wherebyabrupt bends which would normally be subjected to the greatest stressesduring expansion and/or contraction are eliminated.

Still another object of this invention is to provide a novel method ofthe type set forth wherein the circular element is tubular and is whollyhoused within the cavity, and the ends of the circular element aretemporarily plugged by a vented insert whereby pressure build-upinternally of the hollow element is precluded during the castingoperation to prevent the rupture thereof.

A further object of this invention is to provide a novel method whereininserts are preferably disposed tangentially to the mold cavity wherebyupon the solidification of the molten metal and the removal of theinsert ends of the hollow element are exposed through tangential voidsin the casting or heater body.

Another object of the present invention is to provide a novel device forthe conductive heating and/or cooling of an article which preferably,though not necessarily, includes an annular metallic casting, the shapeof the casting depending upon the desired use of the device, a hollowelement substantially encapsulated by the casting, a portion of thehollow element being exposed by a void in the casting, and meansmounting the hollow element for relative sliding movement relative tothe casting whereby differential, expansion and/or contraction of thehollow element and the metallic casting precludes the hollow elementfrom being damaged.

A further object of the present invention is to provide a novel deviceof the type heretofore mentioned wherein the hollow element is tubularand circular, and the mounting means includes a plurality of sleevesexteriorly surrounding the hollow element and being embedded within thecasting. I

Another object of this invention is to provide a novel heater device ofthe type mentioned wherein terminal end portions of the hollow elementare disposed in generally tangential relationship to the casting whichis of a generally angular configuration, and the ends of the hollowelement are in communication with atmosphere through tangential voids inthe outer peripheral surface of the annular casting.

With the above and other objects in view that willhereinafter appear,the nature of the invention will be more clearly understood by referenceto the following detailed description, the appended claimed subjectmatter, and the several views illustrated in the accompanying drawings.

In the drawings:

FIG. 1 is a side elevational view of a mold in which the conductiveheater or matrix of the present invention is formed, with portionsthereof being shown in section for clarity, and illustrates an annularcavity within which is supported a generally circular hollow tubularelement.

FIG. 2 is a top plan view taken along line 2-2 of FIG. 1, andillustrates a plurality of means mounting the hollow element for slidingmovement relative to the mold cavity, as well as the casting eventuallyformed therein, and also illustrates tangentially disposed ends of thehollow element closed by venting plugs.

FIG. 3 is an enlarged fragmentary sectional view taken generally alongline 33 of FIG. 2, and illustrates one of the mounting means in the formof a sleeve exteriorly surrounding a portion of the hollow element andbeing supported within the cavity by a removable bolt passed throughaperture in the mold and threaded into a nut welded to the sleeve.

FIG. 4 is a fragmentary top plan view of the mold of FIG. 2, andillustrates a modification wherein the ends of the circular hollowtubular element are radially disposed with respect to the mold and aremounted for relative sliding movement by asbestos sleeves housed withinradial openings of the mold body.

I FIG. 5 is a side elevational view of two matrix halves formed in themold of FIGS. 1 and 2, with portions thereof removed for clarity, andillustrates the manner in which the halves define a matrix cavity inwhich an article may be heated and/or cooled by introducing a heatedmedium into the hollow elements through the exposed ends or insertingtherein a heater adapted for connection to a source of electricalenergy.

FIG. 6 is a fragmentary sectional view taken generally along line 6--6of FIG. 5, and illustrates the manner in which fitments are secured toexposed ends of the hollow elements through tangential voids or openingsin the outer peripheral surface of each of the matrix halves. I

FIG. 7 is an enlarged fragmentary sectional view similar to FIG. 6, andillustrates a heating element housed within the tubular element withends thereof exposed for connection to a source of electrical energy.

Reference is first made to FIGS. 1 through 3 of the drawings whichillustrate a mold 10 formed by an upper mold half 11 and a lower moldhalf 12.

The upper mold half 11 includes a generally circular plate l3.having atits axis a tubular gate 14 in which molten metal is poured to fill acavity 15 defined by the lower mold half 12. About the periphery(unnumbered) of the plate 13 of the upper mold half 11 are disposed aplurality of circumferentially spaced tubular risers 16 that feed thecasting as it solidifies in a conventional manner. There are six suchrisers 16 equally spaced about the periphery of the plate 13, but thenumber thereof may vary depending upon .the size, shape, design, etc. ofthe mold cavity 15. Suitable means (not shown) are connected to tie bars17 for lifting and lowering the upper mold half 11 relative to the lowermold half 12 which may be conventionally supported on a level floor,table or like support S.

The lower mold half 12 includes a central generally circular core 18having an axial recess 20 in axial alignment with the axis of the gate14. Radiating radially outwardly of the recess 20 are six channels 21,each of which is in alignment with one of the risers 16. The channels 21open into the cavity 15 which is defined by a generally curvedperipheral surface 22 of the core 18, a lower flat annular surface 23 ofa flange 24 of the core 18, and an inner surface 25 of an outer annularwall 26.

Prior to positioning the upper mold half 11 upon an upper surface 27 ofthe outer annular wall 26 in the manner illustrated in phantom outlinein FIG. 1, a hollow, tubular, generally circular element E is supportedinteriorly of the cavity 15 by a plurality of identical mounting means,each of which is generally designated by the reference numeral 30 inFIGS. 1 through 3 of the drawings. As is best illustrated in FIG. 2, themounting means 30 are spaced from each other about the periphery of thewall 26 and are supported thereby in a manner which will be bestunderstood by reference to FIGS. 2 and 3 of the drawings in particular.

Each of the mounting means 30 includes a hollow annular sleeve 31 towhich is welded or otherwise conventionally. secured a nut 32 into whichis threaded an end portion 33 of a bolt 34 (FIG. 3).'The bolt 34 passesthrough an opening 35 of the outer wall 26 and terminates at theexterior thereof in a bolthead 36. The 3 bolt 34 preferably forms afriction fit with the opening 35 so that molten metal introduced intothe cavity 15 will be incapable of passing through the space between thebolt 34 and the passage. 35 to the exterior of the outer wall 26. As analternative, suitable packing or sealing material may be positionedbetween the bolt 34 and the passage 35 to prevent the leakage of moltenmetal.

A plate 37 constructed from flexible metallic material includes acentral opening 38 through which passes the bolt 34. The bolt head 36rests against an outer face (unnumbered) of the plate 37. Opposite ends(unnumbered) of the plate 37 are provided with threaded apertures(unnumbered) and in each of which is threadably secured an Allen screw40.

The mounting means 30 andthe hollow element E are assembled by firstsliding each of the sleeves 31 carrying the nuts 32 upon the hollowelement E by merely telescoping the same over terminal ends 41, 42 ofthe hollow element E. At this time the bolts 34 are not threaded in thenuts 32, and the sleeves 31 are merely slid upon the hollow element E togenerally the position thereof illustrated in FIG. 2. Thereafter thebolts 34 are inserted through the apertures 38 of the plate 37 and eachpassage 35 after which each bolt is threaded into an associated nut 32.Thereafter the screws 40 are threaded to the position shown in FIG. 2 tocenterthe hollow element E within the cavity 15 in themanner-illustrated in FIGS. 1 and 2, it being noted at this time thatthe ends 41, 42 are housed within the cavity l5 in generallysuperimposed relationship to each other. Ob-

viously, if molten metal or similar flowable. but solidifiable materialwerepoured into the cavity 15, the same would enter the end portions 41,42 which is obviously undesirable. Therefore, the ends 41,42 arepreferably provided with internal threads 43 (FIG. 6) and threaded intoeach end portion 41, 42 is an externally threaded steel plug 44 havingan axial bore 45. The plugs 44 are inserted through tangential bores 46(FIG. 2) in the outer wall 26 and thus place the interior of the hollowelement E in fluid communication with atmosphere. Here again the plugsor inserts 44 are preferably in. frictional engagement with the surfaceof the bores 46 to prevent the molten metal from escaping through thebore 46, but if necessary or desirable suitable sealing material, suchas asbestos, may be positioned between the bore 46 and the exterior ofthe inserts 44 to prevent the escape of the molten metal outwardly ofthe cavity 15. As is best illustrated in FIG. 2, ends of the inserts 44project into the cavitylS and the axis of each insert 44 is coincidentto the axis of the associated end portions 41, 42 of the hollow elementE.

After the hollow element E has been positioned in the cavity in themanner illustrated in FIG. 2, the upper mold half 11 is descended to thephantom outline position shown in FIG. 1 and molten metal, such asaluminum, is poured into the gate 14 and flows through the channels 21filling the cavity 15 and the risers 16 in a conventional manner. Theelevated temperature of the molten metal may produce steam or othergases internally of the hollow element E, and these are vented toatmosphere through the passages 45 of the inserts 44. Moreover, assumingthat the hollow element E is formed of steel or any other materialhaving a coefficient of expansion different from that of the aluminum orother molten metal, any relative expansion and/or contraction of thehollow element E relative to the metal in the cavity 15, as the lattersolidifies, is compensated for by the sliding movement permitted to thehollow element E relative to the sleeves 31. Moreover, should the hollowelement E expand to increase its normal diameter, the bolts 34 are freeto move radially outwardly while during contraction of the hollowelement E to a diameter less than its original diameter the resilientnature of the plates 37 permit the same to deflect to an outwardlyopening bowed configuration thus permitting any contraction of thehollow element E. Moreover, the sleeves 31 are so closely fit upon thehollow element E that the molten metal cannot enter between the exteriorsurface of the hollow element E and the interior surface of each sleeve31, and upon solidification of the molten metal relative slidingmovement between the hollow element E and each of the sleeves 31 iseffected when in use, as will be hereinafter more fully described. Topositively assure such sliding movement an asbestos sleeve may bepositioned between the tubular element E and each sleeve 31 thuspreventing the molten metal from flowing between the hollow element Eand the sleeves 31 during the casting operation.

After the casting has solidified and cooled the upper mold half 11 isremoved and subsequently any excess material, as may have solidified inthe riser 16 or the gate 14, is removed in a conventional manner.However, this is done only after the casting, which is generallydesignated by the reference numeral 50 in FIG. 5, has been removed fromthe lower mold half 12. In order to accomplish the removal of thecasting 50 from the cavity 15, the bolts 34 are unthreaded from the nuts32 which, due to the hexagonal outline thereof, are embedded in thecasting and cannot rotate.

Thus, each bolt 34 may be removed to free each casting from the outerwall 26 with the sleeves 31 and the bolts 32 embedded within the casting50. Thereafter, the inserts 44, 44 are unthreaded from the end portions41, 42 of the hollow element E and the outer wall 26, which may be of asectional construction, i.e., two semi-annular halves, is removed topermit the removal of the casting 50 from the cavity 15 for subsequentfinishing and machining, as might be necessary.

Reference is now particularly made to FIG. 5 wherein two of the castings50, 50 formed in the mold 10 are illustrated, with the castings beingpositioned one atop the other to define a matrix which is generallydesignated by the reference numeral 51 having an outer peripheralsurface 52 and an inner peripheral surface 53 defining a cavity 54adapted to receive a tire for subsequent recapping, vulcanizing and thelike. The castings 50, 50 are suitably secured to each other during arecapping operation.

By virtue of the use of the inserts 44, 44 during the molding of thecastings 50, the same are provided in the peripheries 52 thereof withvoids or recesses 55-, 56, each of which has an axis in coincidence.with the respective end portions 41, 42 of the hollow element E. If, forexample, the matrix 51 is to be heated by steam, hot water or similarheated media, a nipple 57 is threaded into each of the thread portions43 of the end portions 41, 42, and steam, hot water, or the like may beintroduced into and removed from the hollow element E in the mannerindicated in FIG. 6. However, if instead it is desired to heat thematrix 51 by electrical energy, a conventional calrod 58 is telescopedthrough the hollow element E and opposite ends thereof 60, 61 aresecured to the interior threads 43 of the hollow element end portions41, 42. Suitable terminals 62, 63 are accessible through the voids 55,56 for connection to an electrical energy source.

The calrod or similar heating element 58 is preferably provided alongits length with a plurality of annular washer-like spacers 64 whichprevent the heating element 58 from actually coming into contact withthe inner walls of the hollow metallic element E. However, the spacers64 are provided with sufficient clearance to allow for the heatingelement 58 to expand and contract. If desired, before the ends 41, 42are closed by the threaded elements 60, 61, the hollow element E may befilled with any good, practical heat transfer agent such as hightemperature, nonflammable oil or powdered metal, such as aluminum orpowdered graphite. Of course, the liquid would be preferable since itwould eliminate any air pockets thereby giving positive heat transfer aswell as protecting the heating element 58 from atmosphere and thuseliminating oxidation.

From the foregoing, and particularly a comparison of FIGS. 6 and 7, itis also to be noted that the castings 50 can be readily converted fromelectrical-type heaters to steam-type heaters merely by interchangingthe heater 58 of FIG. 7 with the nipples 57 of FIG. 6. Thisconvertibility is highly desirable. Furthermore, due to the absence ofbends in the hollow element E, the heating element 58 can be readilyinserted completely through the hollow element E after the castings 50,50 have been formed, and need not be housed in the hollow element Eduring the casting operation wherein the elevated temperatures of themolten metal could adversely affect the same.

Though the absence of abrupt bends is an important object ofconstructing the castings 50, 50 in the manner heretofore described,reference is made to FIG. 4 I

which illustrates a mold identical to the mold of FIGS. 1 though 3,except in the present case a side wall 66 thereof is provided withradial passages or bores 67, 68 through which project radial terminalends 70, 71 of another hollow tubular element E. The end portions 70, 71are preferably wrapped in asbestos or asbestos sleeves 72 to prevent themolten metal from flowing outwardly through the passages 67, 68, as wellas to permit the end portions 70, 71 to slide radially in the passages67, 68 during expansion or contraction of the tubular element E.Furthermore, though the end portions 70, 71 are illustrated as integralportions of the circular hollow element E, the same may be separatepieces or fitments welded to the hollow element E at the 90 bendthereof. Whereas such conventionally welded structures might rupture dueto expansion and contraction when in use, the manufacture of the castingin the manner heretofore described which permits the relative slidingmovement due to the sleeves 31 will virtually preclude such rupture atthe welds. Thus, though not illustrated in FIGS. 4 and 5, the hollowelements E and E include within the castings 50, 50, the sleeves 31 andthe nuts 32 to permit the contraction and expansion heretofore noted.

While the present invention has been described particularly in themanufacture of annular. matrices 51 or similar heating devices, themanner in which relative movement of the hollow element E relative to acasting by virtue of the sleeve 31 being embedded therein may beemployed in any type of heating device. As an example, a mold could beconstructed of a generally triangular configuration with a likecontoured hollow element being disposed therein and supported bycomparable mounting means 30. When the casting formed therein hassolidified an electrical heater could be installed, as in the case ofFIG. 7, to use the casting as the base of a conventional electric iron.Moreover, by merely molding completely solid circular or rectangularplates one could construct such appliances a hot-plates, percolatorheaters, etc., merely by incorporating therein comparable electricheating devices, such as the heating device 58. However, in any suchcase the relative sliding movement provided between the hollow elementsand the casting body per se by virtue of the embedded sleeve 31precludes damage irrespective of the differences in coefficients ofexpansion between the material from which the hollow elements areconstructed and the casting material.

Though the hollow element E has been described as being preferablyformed of steel while the molten metal introduced into the cavity hasbeen described as aluminum, it is to be understood that changes in thesematerials are within the scope of this invention. For example, thehollow elements B may be formed of copper and for that matter need notbe constructed from metallic material as also need not the moltenmaterial introduced into the cavity 15. Insofar as the present inventionis concerned, the hollow elements E may be constructed of most any typematerial so long as the melting point thereof is higher than the meltingpoint of the molten material poured into the mold 15 While preferredforms and arrangements of parts have been shown in illustrating theinvention, it is to be clearly understood that various changes indetails and arrangement of parts may be made without departing from thespirit and scope of this disclosure.

lclaim:

l. A method of manufacturing a casting comprising the steps of providinga mold having a cavity of a predetermined configuration, positioning anelement wholly within said cavity, supporting said element for slidingmovement relative to said cavity, filling said cavity with flowablematerial, solidifying said flowable material whereby said relativesliding movement is provided at least during the solidification of saidflowable material, and including the step of preventing the of ventingthe interior of the hollow elementto atmosphere at least during thesolidification of the flowable material. I

3. A method of manufacturing a casting comprising the steps of providinga mold having a cavity of a predeterminedconfiguration, positioning anelement wholly within said cavity, supporting said element for slidingmovement relative to said cavity, filling said cavity with flowablematerial, solidifying said flowable material whereby said relativesliding movement is provided at least during the solidification of saidflowable material, said cavity is of an annular configuration, saidelement is of a circular configuration, and said method includes thefurther step of preventing the flowable material from entirelyencapsulating the element whereby a portion thereof is exposed through avoid of the solidified material.

4. The mold as defined in claim 3 wherein said preventing step isperformed by positioning an insert 'against said end portion in spanningrelationship to a portion of said cavity and into said mold prior tofilling the cavity with the flowable material.

5. The mold as defined in claim 4 wherein said circular element ishollow and said insert includes an opening for venting the circularelement to atmosphere during the formation of the casting. y

6. The mold as defined in claim 4 wherein the end portion of thecircular element is-in generally tangential relationship to the annularmold cavity.

7. A method of manufacturing a casting comprising the steps of providinga mold having a cavity of a predetermined configuration, positioning ahollow element wholly within the cavity, placing the hollow element influid communication with atmosphere by means of a hollow member at leastpartially'spanning said cavity and opening to atmosphere, filling saidcavity with flowa ble material to encapsulate a major portion of thehollow element and a portion of the hollow member, solidifying theflowable material, and removing the hollow member from the hollowelement and the solidified material thereby forming a void in the latterthrough which is rendered accessible the interior of the hollow element.

8. The method as defined in claim 7 wherein said cavity is of an annularconfiguration and said hollow member is of a generally circularconfiguration having opposite ends, and the step of placing the hollowelement in fluid communication with atmosphere is performed bytemporarily securing the hollow member to at least one of said oppositeends.

9. The method as defined in claim 8 wherein said at least one end isdisposed in generally tangential relationship to said annular cavity.

10. A method of manufacturing a casting comprising the steps ofproviding a mold having a cavity of a predetermined configuration,assembling a plurality of individual sleeves in external telescopicsliding relationship to an element, positioning said sleeves and atleast a portion of said element in the cavity, supporting each sleeveindividually by a rod secured thereto passing through said mold, fillingthe cavity with hot flowable material having a coefficient of expansiondifferent than that of said element, and solidifying said flowablematerial whereby relative sliding movement is provided during and afterthe solidification thereof.

11. The method as defined in claim 10 including the step of sliding thesleeves individually along the element for assembly as well as forpositioning each sleeve relative to its associated supporting rod.

12. The method as defined in claim 11 wherein said cavity is of anannular configuration, said element is of a generally circularconfiguration, and ends of said circular element project tangentiallyoutwardly of said cavity.

13. The method as defined in claim 10 wherein said element is whollyhoused within said cavity and including the step of preventing theflowable material from entirely encapsulating the element whereby aportion thereof is exposed through a void of the solidified material.

14. The method as defined in claim 10 wherein said element is hollow andis wholly housed within said cavity, and including the step of ventingthe interior of the hollow element to atmosphere at least during thesolidification of the flowable material.

15. The method as defined in claim 10 wherein said cavity is of anannular configuration, said element is of a circular configuration, saidelement is wholly housed within said cavity, and said method includesthe further step of preventing the flowable material from entirelyencapsulating the element whereby a portion thereof is exposed through avoid of the solidified material.

16. The method as defined in claim 10 including the step ofdisassembling the sleeves and rods after the solidification of saidflowable material.

17. The method as defined in claim 16 including the step of threadedlysecuring each sleeve to its associated rod whereby disassembly thereof 4occurs through an unthreading action.

18. A method of manufacturing a casting comprising the steps ofproviding a mold having a cavity of a predetermined configuration,positioning an element wholly within said cavity, filling said cavitywith flowable material, said cavity being of an annular configurationand said element is of a generally circular hollow configuration,preventing the flowable material from entirely encapsulating theelement, said last-mentioned step being performed by plugging the endsof the hollow element with a member which at least partially spans thecavity, and solidifying said flowable material.

19. The method as defined in claim 18 wherein said plugging membersproject tangentially outwardly of said cavity thereby defining generallytangential voids upon the removal thereof from the exterior of thecasting.

1. A method of manufacturing a casting comprising the steps of providinga mold having a cavity of a predetermined configuration, positioning anelement wholly within said cavity, supporting said element for slidingmovement relative to said cavity, filling said cavity with flowablematerial, solidifying said flowable material whereby said relativesliding movement is provided at least during the solidification of saidflowable material, and including the step of preventing the flowablematerial from entirely encapsulating the element whereby a portionthereof is exposed through a void of the solidified material.
 2. Amethod of manufacturing a casting comprising the steps of providing amold having a cavity of a predetermined configuration, positioning anelement wholly within said cavity, supporting said element for slidingmovement relative to said cavity, filling said cavity with flowablematerial, solidifying said flowable material whereby said relativesliding movement is provided at least during the solidification of saidflowable material, said element is hollow, and including the step ofventing the interior of the hollow element to atmosphere at least duringthe solidification of the flowable material.
 3. A method ofmanufacturing a casting comprising the steps of providing a mold havinga cavity of a predetermined configuration, positioning an element whollywithin said cavity, supporting said element for sliding movementrelative to said cavity, filling said cavity with flowable material,solidifying said flowable material whereby said relative slidingmovement is provided at least during the solidification of said flowablematerial, said cavity is of an annular configuration, said element is ofa circular configuration, and said method includes the further step ofpreventing the flowable material from entirely encapsulating the elementwhereby a portion thereof is exposed through a void of the solidifiedmaterial.
 4. The mold as defined in claim 3 wherein said preventing stepis performed by positioning an insert against said end portion inspanning relationship to a portion of said cavity and into said moldprior to filling the cavity with the flowable material.
 5. The mold asdefined in claim 4 wherein said circular element is hollow and saidinsert includes an opening for venting the circular element toatmosphere during the formation of the casting.
 6. The mold as definedin claim 4 wherein the end portion of the circular element is ingenerally tangential relationship to the annular mold cavity.
 7. Amethod of manufacturing a casting comprising the steps of providing amold having a cavity of a predetermined configuration, positioning ahollow element wholly within the cavity, placing the hollow element influid communication with atmosphere by means of a hollow member at leastpartially spanning said cavity and opening to atmosphere, filling saidcavity with flowable material to encapsulate a major portion of thehollow element and a portion of the hollow member, solidifying theflowable material, and removing the hollow member from the hollowelement and the solidified material thereby forming a void in the latterthrough which is rendered accessible the interior of the hollow element.8. The method as defined in claim 7 wherein said cavity is of an annularconfiguration and said hollow member is of a generally circularconfiguration having opposite ends, and the step of placing the hollowelement in fluid communication with atmosphere is performed bytemporarily securing the hollow member to at least one of said oppositeends.
 9. The method as defined in claim 8 wherein said at least one endis disposed in generally tangential relationship to said annular cavity.10. A method of manufacturing a casting comprising the steps ofproviding a mold having a cavity of a predetermined configuration,assembling a plurality of individual sleeves in external telescopicsliding relationship to an element, positioning said sleeves and atleast a portion of said element in the cavity, supporting each sleeveindividually by a rod secured thereto passing through said mold, fillingthe cavity with hot flowable material having a coefficient of expansiondifferent than that of said element, and solidifying said flowablematerial whereby relative sliding movement is provided during and afterthe solidification thereof.
 11. The method as defined in claim 10including the step of sliding the sleeves individually along the elementfor assembly as well as for positioning each sleeve relative to itsassociated supporting rod.
 12. The method as defined in claim 11 whereinsaid cavity is of an annular configuration, said element is of agenerally circular configuration, and ends of said circular elementproject tangentially outwardly of said cavity.
 13. The method as definedin claim 10 wherein said element is wholly housed within said cavity andincluding the step of preventing the flowable material from entirelyencapsulating the element whereby a portion thereof is exposed through avoid of the solidified material.
 14. The method as defined in claim 10wherein said element is hollow and is wholly housed within said cavity,and including the step of venting the interior of the hollow element toatmosphere at least during the solidification of the flowable material.15. The method as defined in claim 10 wherein said cavity is of anannular configuration, said element is of a circular configuration, saidelement is wholly housed within said cavity, and said method includesthe further step of preventing the flowable material from entirelyencapsulating the element whereby a portion thereof is exposed through avoid of the solidified material.
 16. The method as defined in claim 10including the step of disassembling the sleeves and rods after thesolidification of said flowable material.
 17. The method as defined inclaim 16 including the step of threadedly securing each sleeve to itsassociated rod whereby disassembly thereof occurs through an unthreadingaction.
 18. A method of manufacturing a casting comprising the steps ofproviding a mold having a cavity of a predetermined configuration,positioning an element wholly within said cavity, filling said cavitywith flowable material, said cavity being of an annular configurationand said element is of a generally circular hollow configuration,preventing the flowable material from entirely encapsulating theelement, said last-mentioned step being performed by plugging the endsof the hollow element with a member which at least partially spans thecavity, and solidifying said flowable material.
 19. The method asdefined in claim 18 wherein said plugging members project tangentiallyoutwardly of said cavity thereby defining generally tangential voidsupon the removal thereof from the exterior of the casting.